Power converters commonly used in optical networks convert AC or DC input power to DC output(s) frequently have multiple outputs that are often derived from multiple transformers within the converters. In converters employing multiple transformers, DC power is commonly derived as a first stage converts commercial AC power into DC power by using an AC/DC converter. Once converted, the power is manipulated in a second stage by a DC/DC converter. This secondary conversion further conditions the power resulting in multiple voltage outputs. Such outputs commonly include voltage values of +5V, +3.3V, -48V and a variable return voltage.
Additionally, typical power converters include a battery backup stage that operates as an alternate power source when commercial AC power fails. The battery backup stage is coupled to both the AC/DC stage and the DC/DC stage. During normal operation, when commercial AC power is online, the battery backup stage operates in a charging mode, where the AC/DC converter supplies power to maintain the charge. When AC power fails, the battery backup stage switches to a discharge mode to supply power from one or more backup batteries to the optical network.
As those skilled in the art are aware, the backup batteries are routinely discharged for testing purposes to ensure performance when needed. Commonly, one battery (the "battery under test") is coupled at a time to a load that dissipates energy supplied to it by the battery under test. In systems using multiple battery backups, one battery is discharged while others remain in a continually charging mode, prepared to supply DC power to the load in case of main power failure.
Unfortunately, when the batteries are discharged through these loads, great amounts of power are wasted. Usually, the energy dissipated appears as heat radiated from the load. Not only is the heat emitted wasteful, it may also be harmful. The traumatic nature of this discharge commonly damages the load and reduces its overall lifetime. Should the load suffer a critical breakdown, the system as a whole could be damaged or destroyed. Additionally, heat generated can possible damage other components in the system or pose a fire hazard to equipment and buildings located in proximity.
Accordingly, what is needed in the art is a power supply which is capable of discharging and testing backup batteries in a manner that is less wasteful and less offensive to the environment.